Ligands with at least a fluorosilcone substituent useful for preparing metal-locenes

ABSTRACT

The invention concerns ligands with at least a fluorosilicone substituent of general formulae (I) and (II); a method for preparing them and their use for producing catalysts useful for olefin polymerisation

FIELD OF THE INVENTION

The present invention relates to ligands (of transition metals) with atleast one fluorosilicone [sic] substituent, to a process for preparingthem and to their use in the preparation of metallocene-type catalystswhich can be used in particular for the polymerization of olefins.

BACKGROUND OF THE INVENTION

Veronica Herrera et al. (Inorganic Chemistry Communications, 1998, pages197 to 199) describe organic complexes of formulae:[η⁵—C₅H₄CH₂CH₂(CF₂)₉CF₃]Rh(CO)L with L=CO or P[CH₂CH₂(CF₂)₅CF₃]₃ andCl₂Ni{P[CH₂CH₂(CF₂)₈CF₃]₃}, which are obtained from the ligandsC₅H₄CH₂CH₂(CF₂)₉CF₃ and P[CH₂CH₂(CF₂)₅CF₃]₃.

Russell P. Hugues et al. (Organometallics, 1966, 15, pages 286 to 294)showed that it was necessary to have, in ligands of theη⁵—C₅H₄(CH₂)_(n)(CF₂)_(m)F type, a hydrocarbon spacer group in order toisolate the cyclopentadienyl ring from the attractive effect of theperfluorinated chains in the abovementioned ligands.

International Application WO 99/54367 discloses catalytic systems ofmetallocene type in which the cyclopentadienyl radical always comprisesat least one substituent of formula:

in which R² represents in particular a fluoroalkyl radical having anumber of carbon atoms ranging from 1 to 25, s is an integer rangingfrom 1 to 20 and r=1, 2, 3, 4 or 5.

DESCRIPTION OF INVENTION

A subject-matter of the invention is compounds of general formulae (I)or [sic] (II):

[A][Si(R)_(3−n)Rf_(n)]_(z)  (I)

in which:

-   -   A represents a cyclopentadienyl, indenyl or fluorenyl radical;    -   R represents a hydrogen atom, a linear or branched alkyl radical        having a number of carbon atoms ranging from 1 to 40, an alkoxy        radical having a number of carbon atoms ranging from 1 to 10, an        aryl radical having from 6 to 20 carbon atoms, an aryloxy        radical having from 6 to 10 carbon atoms or an alkenyl radical        having a number of carbon atoms ranging from 2 to 10;    -   Rf represents a perfluoroalkyl radical C_(x)F_(2x+1)—(CH₂)_(y)—        in which x represents an integer ranging from 1 to 20 and y=0,        1, 2 or 3;    -   n=1, 2 or 3;    -   z is equal to 1, 2 or 3;    -   B represents a divalent group >MR¹R² or else    -    in which M represents a carbon atom, a silicon atom, a        germanium atom or a tin atom; R¹, R², R³ and R⁴, which are        identical or different, represent a hydrogen atom, a linear or        branched alkyl radical having a number of carbon atoms ranging        from 1 to 20 or an aryl radical having from 6 to 14 carbon        atoms; preferably, B represents divalent groups such as:        —(CH₂)₂—, —CH(CH₃)—CH₂—, —CH(C₄H₉)C(CH₃)₂—, —CH₂Si(CH₃)₂— or        >Si(CH₃)₂;    -   C represents a cyclopentadienyl, methylcyclopentadienyl,        pentamethylcyclopentadienyl, butylcyclopentadienyl, indenyl,        naphthyl or fluorenyl radical;    -   w=1 or 2.

Preference is given, among the compounds of formulae (I) and (II), tothose in the formulae of which A represents a cyclopentadienyl radical,R represents a CH₃— and Rf represents a perfluoroalkyl radicalC_(x)F_(2x+1)(CH₂)_(y)— in which x ranges from 1 to 8 and y=0 or 2.

Preferably, Rf=CF₃(CF₂)₅(CH₂)₂— or CF₃(CF₂)₇—; n=1; z=1 or 2;B=>Si(CH₃)₂; and w=2.

Mention will be made, by way of illustration of compounds of formula(I), of:

-   -   dimethyl(1H,1H,2H,2H-perfluoro-1-octyl)silylcyclopentadiene,    -   dimethyl(perfluorooctyl)silylcyclopentadiene,    -   1,3-bis[dimethyl(perfluorooctyl)silyl]cyclopentadiene.

Mention will be made, by way of illustration of compounds of formula(II), of the compounds of formula:

(CH₃)₂Si[C₅H₄Si(CH₃)₂C₈F₁₇]₂

(CH₃)₂Si[C₅H₃{Si(CH₃)₂C₈F₁₇}₂]₂

The compounds of formula (I) in the formulae of which y is other than 0can be prepared according to the following reaction scheme:

with Rf=C_(x)F_(2x+1)(CH₂)_(y)—;X=Cl, Br or I and z=1, 2 or 3.

The reaction (1) is carried out in a known way, which consists inpreparing the lithiated derivative 2 in a nonpolar solvent, such ashexane, by reacting 1 with butyllithium at a temperature between 0° C.and 20° C. for several hours. On completion of the reaction, thereaction solvent is removed and then the product obtained is dried underreduced pressure. The reaction is carried out under a nitrogenatmosphere and in the absence of moisture.

As regards the reaction (2), it is carried out according to noncriticalconditions, which consist in dissolving the lithiated derivative 2 in anether, such as THF, at low temperature and then the addition is carriedout [sic] to the solution obtained of an ethereal solution ofperfluorohaloalkylsilane 3 [sic] maintained at a temperature in theregion of 0° C., the said halochlorosilane [sic] preferably being usedin a molar excess of 1% to 10% with respect to the stoichiometry of thereaction (2).

The reaction is subsequently continued for several hours at ambienttemperature with stirring, the volatile compounds are then removed underreduced pressure and the product (I) obtained is extracted by means ofan inert solvent and then distilled under reduced pressure.

Use is preferably made of the perfluoroalkylchlorosilanesRf_(n)Si(R)_(3−n)Cl, which can be obtained according to a methoddescribed in J. Fluorine Chem., 44, page 191, 1955.

The compounds of formula (I) in the formulae of which y=0 can beobtained according to the reactions below:

n=1, 2 or 3; z=1, 2 or 3.

The reaction (3) is carried out according to a process which consists inslowly adding a solution of BuLi in hexane to a mixture composed ofC_(x)F_(2x+1)I and of a molar excess of HSi(R)_(3−n)Cl_(n), with respectto the molar amount of C_(x)F_(2x+1)I employed, in ether at −78° C.

The compounds of formula (II) can be obtained according to knownmethods, which consist in reacting the lithiated compounds (I) and/or(C) in a solvent medium with a dichlorinated compound BCl₂.

Another subject-matter of the invention is the use of the compounds offormula (I) or (II) as ligands of metals of Group (III) [sic], IVb, Vbor VIb, of the lanthanides or of the actinides of the Periodic Table inthe preparation of metallocenes of formulae:(C′

_(2−w)M¹Lt

I′)_(w)  (III)

in which (B) and w have the same meanings as in the abovementionedformulae (I) and (II);(I′) represents (I) in which the radical (A) has one hydrogen less, (C′)represents (C) with one hydrogen less;

-   -   D=(C′) or (I′);    -   M¹ represents a metal from Groups III, IVb, Vb or [sic] VIb and        a metal from the group of the lanthanides or actinides;    -   L, which is identical or different, represents a halogen atom, a        linear or branched alkyl radical having a number of carbon atoms        ranging from 1 to 20, an alkenyl radical having from 2 to 20        carbon atoms, an alkoxy radical having from 1 to 20 carbon atoms        or an aryloxy or aryl radical having from 6 to 40 carbon atoms;    -   t represents an integer ranging from 1 to 4 and is equal to 2        when, in the formulae (III) and (IV), M¹=Ti, Zr or Hf.

Preferably, M¹ represents a metal from Group IVb and, very particularly,M¹ represents Zr.

The compounds of formula (III) or (IV) can be obtained according toknown methods, which consist in introducing the lithiated derivative of(I) or of (II), in solution in an ether, such as THF, dropwise at lowtemperature into an ethereal solution of M¹L_(t) at approximately 0° C.,then reaction is allowed [sic] to take place at ambient temperature withstirring for several hours and the compounds (III) or [sic] (IV) areisolated [sic] according to methods known to a person skilled in theart.

Another subject-matter of the present invention is a process for theproduction of polyolefins by polymerization of at least one olefin inthe presence of a catalyst which comprises at least one compound offormula (III) or (IV) as precatalyst and at least one cocatalyst.

The polymerization can be a homopolymerization or a copolymerization.

According to the present invention, preference is given to thehomopolymerization or the copolymerization of olefins of formula:

R^(α)—CH═CH—R^(β), in which R^(α) and R^(β), which are identical ordifferent, represent a hydrogen atom, a halogen atom, a linear orbranched hydrocarbon radical having a number of carbon atoms rangingfrom 1 to 20 and preferably ranging from 1 to 10 or a phenyl radicaloptionally substituted by a halogen atom or a linear or branched alkylradical having a number of carbon atoms ranging from 1 to 4; R^(α) andR^(β) can also, together with the atoms connecting them, form one ormore rings.

Mention will be made, by way of illustration of such olefins, of1-olefins, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene,1-octene or 4-methyl-1-pentene; styrene; dienes, such as 1,3-butadieneor 1,4-butadiene; or cycloolefins, such as norbornene,tetracyclododecene, norbornadiene or vinylnorbornene.

The polymerization process of the invention applies very particularly tothe homopolymerization of ethylene.

The polymerization can be carried out in a known way in the gas phase orin a liquid reaction medium; an inert solvent or the olefin (to bepolymerized) can be used as reaction medium.

The polymerization can be a solution, suspension, emulsion or bulkpolymerization, a gas-phase polymerization or a polymerization in asupercritical medium (CO₂). It can be carried out either continuously orbatchwise, at high pressures ranging from 50 to 300 MPa (bar) and at lowpressures ranging from 0.01 to 50 MPa. The polymerization can be carriedout at temperatures ranging from 0° C. to 250° C. and preferably rangingfrom 50° C. to 150° C.

The catalyst which comprises at least one compound of formula (III) or(IV) of the present invention can be used in a homogeneous phase or canbe supported.

Mention will be made, as support which can be used according to thepresent invention, of silica gels, fluorinated silica, highly dividedpolyolefin powder or inorganic oxides, such as alumina or silica.

The catalyst used in the present invention preferably comprises, asprecatalyst, a metallocene of formula (III) or (IV) and a cocatalyst. Itis possible to use a mixture of at least 2 or more metallocenes (III) or(IV), in particular when a reasonably broad molecular distribution isdesired.

Mention will be made, as cocatalyst which can be used according to thepresent invention, of Lewis acids, such as BF₃, organoboron compounds,such as tris(4-fluorophenyl)borane or tris(pentafluorophenyl)borane, ororganoaluminium compounds, such as aluminoxanes, represented by thegeneral formulae for the linear compounds:

and for the cyclic compounds:

in which the R⁵ radicals, which can be identical or different, representa hydrogen atom, a linear or branched alkyl radical having a number ofcarbon atoms ranging from 1 to 20, a fluoroalkyl radical having a numberof carbon atoms ranging from 1 to 6, an aryl radical having from 6 to 18carbon atoms or a fluoroaryl radical having from 6 to 18 carbon atomsand p can be equal to 0 or represents an integer ranging from 1 to 50.

The aluminoxanes are also available commercially. Thus, Aldrich sells,for example, methylaluminoxanes as a 10% by weight solution in toluene.

Use will preferably be made of aluminoxanes in the formulae of which theR⁵ radicals are identical and represent a methyl, an isobutyl or aphenyl and very particularly a methyl.

The proportions of metallocenes (III) or [sic] (IV) and of cocatalystsconstituting the polymerization catalyst can vary to a large extent. Acocatalyst/transition metal M¹ molar ratio ranging from 1/1 to 10 000/1and preferably ranging from 1/1 to 1 000/1 will be used.

The metallocenes (III) or [sic] (IV) of the present invention can beused according to concentrations based on the transition metal M¹ whichrange from 10⁻³ to 10⁻⁸ mol, preferably from 10⁻⁴ to 10⁻⁷ mol, of metalM¹ per litre of solvent.

The use of the metallocenes (III) and/or (IV) of the present inventionin processes for the polymerization of olefins makes it possible topolymerize olefins with a good productive output.

The examples which follow illustrate the invention.

EXAMPLES

The following reactants are used:

-   -   cyclopentadiene was obtained by cracking dicyclopentadiene and        is distilled before use;    -   chloro(dimethyl)(1H,1H,2H,2H-perfluoro-1-octyl)silane was        obtained according to a process described in J. Fluorine Chem.,        44, page 191, 1995;    -   all the other reactants are commercially available and are used        without purification;    -   the solvents are dried and distilled before their use. The        compounds obtained were characterized by elemental analysis and        by ¹H, ¹³C, ²⁹Si and ¹⁹F NMR.

All the reactions are carried out under a dry nitrogen atmosphere.

The NMR spectra were recorded on a Varian Inova 300 or Varian Mercury200 device.

Mass spectrometry (nano ES-Q-TOF-MS) was carried out on a MicromassQ-Tof hybrid tandem mass spectrometer and Mass Lynx software, version3.0.

Preparation ofdimethyl(1H,1H,2H,2H-perfluoro-1-octyl)-silylcyclopentadiene

2.4 ml (29.1 mmol) of freshly distilled cyclopentadiene are added to asolution of n-BuLi (30.4 mmol) in hexane (100 ml), stirred andmaintained at 0° C. The reaction mixture obtained is stirred at ambienttemperature for 3 hours, the solvent is then removed and the productobtained is washed 3 times with pentane (3×50 ml) and is dried underreduced pressure.

The cyclopentadienelithium obtained is dissolved in 100 ml of THF at−78° C. and the solution is added dropwise over 30 minutes to a solutionof C₆F₁₃C₂H₄Si(CH₃)₂Cl (13 g (29.5 mmol) in 100 ml of THF), maintainedat 0° C.

The reaction medium is subsequently stirred at ambient temperature forapproximately 12 hours. The volatile compounds are removed under reducedpressure. The product is extracted with 100 ml of pentane, dried underreduced pressure and then distilled.

10.94 g of an orangy liquid with a boiling point of 75-80° C. under 0.4mmHg are obtained (yield: 80% with respect to the cyclopentadieneemployed).

¹H NMR (CDCl₃) δ (ppm): 6.87 and 6.71 (2×m, CH═, 1- and2-C₅H₅SiMe₂R_(f)), 6.63 and 6.53 (2×m, CH═, 5-C₅H₅SiMe₂R_(f)), 3.40 (m,5-CH, 5-C₅H₅SiMe₂R_(f)), 3.04 (m, 5-CH₂, 1- and 2-C₅H₅SiMe₂R_(f)), 1.98(m, CH₂—CF₂, 1-, 2- and 5-C₅H₅SiMe₂R_(f)), 0.88 (m, CH₂—Si, 1 and2-C₅H₅SiMe₂R_(f)), 0.68 (m, CH₂—Si, 5-C₅H₅SiMe₂R_(f)), 0.21 (s, SiMe₂,1- and 2-C₅H₅SiMe₂R_(f)), 0.03 (s, SiMe₂, 5-C₅H₅SiMe₂R_(f)).

The complexity of the proton NMR spectrum is due to the presence of the1-, 2- and 5-(1H,2H,2H,2H-perfluoro-1-octyldimethylsilyl)cyclopentadiene[sic] isomers, it being understood that the 5 isomer is predominant atambient temperature.

Elemental analysis calculated for C₁₅H₁₅F₁₃Si: C: 38.30; H: 3.19; F:52.55; Si: 5.96. Found: C: 38.08; H: 3.29; F: 52.74; Si: 5.81.

Preparation of1,1′-bis[dimethyl(1H,1H,2H,2H-perfluoro-1-octyl)silylcyclopentadienyl]zirconiumdichloride

37 g (78.7 mmol) of C₅H₅Si(CH₃)₂C₂H₄C₆F₁₃ are added to a solution,stirred and maintained at 0° C., of n-BuLi (78.9 mmol) in hexane (200ml). The mixture obtained is stirred at ambient temperature for 3 hours.The solvent is subsequently removed and the product is washed withpentane (3×50 ml) and subsequently dried under reduced pressure.

The Li[C₅H₄Si(CH₃)₂C₂H₄C₆F₁₃], cooled to −78° C., is dissolved in 100 mlof pre-cooled THF. A solution of 9.08 g (38.2 mmol) of ZrCl₄ in 100 mlof THF is prepared according to a method described [lacuna] Journal Am.Chem. Soc., 1995, Vol. 117, page [sic] 12114-12129. The solution ofLi[C₅H₄Si(CH₃)₂C₂H₄C₆F₁₃] in THF is added dropwise over 30 minutes tothe solution of ZrCl₄ in THF, cooled to 0° C.

The solution obtained is stirred at ambient temperature for 48 hours.The volatile products are removed under reduced pressure and the residueis extracted with 100 ml of refluxing toluene.

The orange-coloured extract is filtered while hot and then the filtrateis concentrated under reduced pressure. 31.5 g of a product in the formof white needles are obtained (yield: 75% with respect to ZrCl₄).

¹H NMR (200.14 MHz, CDCl₃) δ (ppm): 6.65 and 6.52 (t, 4H,J_(AX)=J_(AX′)=2.6 Hz, CH═), 1.98 (m, 2H, CH₂—CF₂), 0.96 (m, 2H,CH₂—Si), 0.37 (s, 6H, (CH₃)₂Si);

¹H NMR (200.14 MHz, d6-acetone) δ [lacuna] 6.81 (s, 4H, CH═), 2.17 (m,2H, CH₂—CF₂), 1.03 (m, 2H, CH₂—Si), 0.40 (t, 6H, J=3.5 Hz, (CH₃)₂Si);

¹³C{H} NMR (50.33 MHz, d6-acetone) [lacuna] 127.24 (CH═), 125.36 (C═),117.21 (CH═), 26.52 (t, ²J_(C,F)=23.3 Hz, CH₂—CF₂), 6.77 (CH₂—Si), −2.25(Si(CH₃)₂);

¹⁹F{H} NMR (282.35 MHz, d6-acetone) δ [lacuna] −77.04 (t, J_(F,F)=9.2Hz, CF₃), −111.52 (m, α-CF₂), −117.81 (s, γ-CF₂), −118.78 (s, δ-CF₂),−119.04 (d, J_(F,F)=12.1 Hz, CF₃), −122.08 Hz (m, β-CF₂);

²⁹Si NMR (59.62 MHz, d6-acetone) δ [lacuna] 1.70 (SiMe₂).

Elemental analysis calculated for C₃₀H₂₈Cl₂F₂₆Si₂Zr; C: 32.73%; H:2.55%; Cl: 6.45%; F: 44.91%; Si: 5.09%. Found: C: 32.58%; H: 2.56%; Cl:6.35%; F: 44.78%; Si: 5.39%.

Mass spectrum (ES): molecular mass calculated for C₃₀H₂₈Cl₂F₂₆Si₂Zr: 1100 g/mol. Found: 1 123 g/mol ([M+Na]⁺).

Preparation of dimethyl(perfluorooctyl)silylcyclopentadiene

C₅H₅Si(CH₃)₂(C₈F₁₇)

1/Preparation of HSi(CH₃)₂C₈H₁₇ [sic] According to the Reaction (3)

50 mmol of butyllithium in 90 ml of hexane are added dropwise over 270minutes to a mixture, maintained at −78° C., comprising 26.52 g ofC₈F₁₇I (48.6 mmol) and 6.8 ml of dimethylchlorosilane in 150 ml ofether.

After having brought the medium to ambient temperature, a whitesuspension is obtained. 50 ml of water and 150 ml of ether are added.

The mixture is settled, the two layers are separated and the ethereallayer is washed with 30 ml of salt water and then dried over MgSO₄.

The solvent is removed on a rotary evaporator; 19.8 g of a yellow oilare obtained, which oil is subjected to distillation under reducedpressure using a 10 cm Vigreux column.

A 10.14 g fraction of HSi(CH₃)₂C₈F₁₇ with a boiling point of 57-59° C.under a pressure of 11 mbar and which comprises, according to ¹⁹F NMR,approximately 5% of C₈F₁₇I is obtained (yield: 44%).

¹H NMR (300.1 MHz, CDCl₃) δ (ppm): 0.38 (d, 6H, ³J_(H,H)=4 Hz,Si(CH₃)₂), 4.24 (broad, 1H, HSi).

¹³C{¹⁹F} NMR (75.5.1 [sic] MHz, CDCl₃) δ (ppm): −7.9 (q, ¹J_(H,C)=125Hz, Si(CH₃)₂), 108.6, 110.5, 111 (s, 2C), 117.7, 117.4 (t, ²J_(F,C)=19Hz, CF₃), 122.7 (CF₂Si).

¹⁹F NMR (282.4 MHz, CDCl₃) δ (ppm): −81.9 (t, 3F, ⁴J_(F,F)=9 Hz, CF₃),−120.8 (broad s, 2F), −122.6 (broad s, 2F), −122.8 (broad s, 4F), −123.6(broad s, 2F), −127.1 (broad s, 2F), −127.6 (d, 2F, ³J_(H,F)=12 Hz,CF₂Si).

²⁹Si{¹H} NMR (59.6 MHz, CDCl₃) δ (ppm): −8.3 (tt, ¹J_(H,C)=125 Hz,Si(CH₃)₂), 108.6, 110.5, 111 (s, 2C), 117.7, 117.4 (t, ²J_(F,Si)=30 Hz,CF₃), ³J_(F,Si)=6 Hz [sic].

2/Preparation of BrSi(CH₃)₂C₈F₁₇ According to the Reaction (4)

A mixture composed of 7.65 [lacuna] of HSi(CH₃)₂C₈F₁₇ (15.8 mmol) and 62mmol of bromine in 25 ml of CCl₄ is stirred at 60° C. for 18 hours.After removing the volatile compounds under reduced pressure, a liquidis obtained and is subjected to flash distillation. 8.35 g ofBrSi(CH₃)₂C₈F₁₇ are obtained (yield 95%, which exists in the form of apale pink liquid) [sic].

¹H NMR (300.1 MHz, CDCl₃) δ (ppm): 0.84 (S); ¹³C{¹⁹F} NMR (75.5 MHz,CDCl₃) δ (ppm): −0.1 (q, ¹J_(H,C)=124 Hz, SiMe₂), 108.6 (partiallyresolved q, J_(H,C)=12 Hz), 110.4, 111.0 (s, 2C), 111.6, 113.0, 117.4(t, ²J_(F,C)=21 Hz, CF₃), 119.3 (CF₂Si).

¹⁹F NMR (282.4 MHz, CDCl₃) δ (ppm): 82.0 (t, 3F, ⁴J_(F,F)=9 Hz, CF₃),−118.8 (broad s, 2F, CF₂Si), −122.5 (broad s, 2F), −122.9 (broad s, 4F),−123.7 (broad s, 2F), −127.2 (m, 4F).

²⁹Si{¹H} NMR (59.6 MHz, CDCl₃) δ (ppm): 17.7 (t, ²J_(F,Si)=35 Hz).

3/Preparation of C₅H₅Si(CH₃)₂C₈F₁₇ According to the Reaction (5)

A solution of 0.93 g of cyclopentadienelithium (12.9 mmol) in 50 ml ofTHF is added dropwise to a stirred solution of 7.32 g of BrSi(CH₃)₂C₈F₁₇(13.1 mmol) in 50 ml of THF at 0° C. The brown solution obtained isstirred for 1 hour after the end of the addition. The reaction israpidly halted by addition of 200 ml of water.

Extraction is carried out with 200 ml of pentane and the organic phaseis washed with water (2 times with 50 ml) and then with 30 ml of saltwater. After drying with magnesium sulphate, the volatile compounds areremoved using a rotary evaporator. The liquid obtained is subjected toflash distillation and 5 g of C₅H₅Si(CH₃)₂(C₈F₁₇) are obtained (yield:70%), which exists in the form of a light-yellow liquid.

¹H NMR (300.1 MHz, CDCl₃) δ (ppm); 0.13 (s, 6H, SiMe₂), 0.51 (s, 1.5H,SiMe₂), 3.18 (d, 0.4H, J=1.5 Hz, C₅H₅), 6.4-7.2 (m, 4.4H, C₅H₅).

¹³C{¹⁹F} NMR (75.5 MHz, CDCl₃) δ (ppm): −7.6 (q, ¹J_(H,C)=121 Hz,SiMe₂), −5.6 (q, ¹J_(H,C)=123 Hz, SiMe₂), 108.7 (partially resolved q,J_(F,C)=12 Hz), 110.5, 111.1 (partially resolved, 2C), 111.8, 113.3,117.4 (t, ²J_(F,C)=16 Hz, CF₃), 123.2, 131.7 (unresolved peak), 133.9(unresolved peak).

¹⁹F NMR (282.4 MHz, CDCl₃) δ (ppm): 81.9 (t, 3F, ⁴J_(F,F)=10 Hz, CF₃),−119.2 (broad s, 2F, CF₂Si), −122.5 (broad s, 2F), −122.7 (broad s, 4F),−123.6 (broad s, 2F), −126.8 (t, 1.5 F, ⁴J_(F,F)=15 Hz, CF₂Si), 127.1(m, 2F), −127.3 (t, 0.5F, ⁴J_(F,F)=15 Hz, CF₂Si).

Preparation of1,1′-bis[dimethyl(perfluorooctyl)silylcyclopentadienyl]zirconiumdichloride

ZrCl₂{C₅H₄Si(CH₃)₂C₈F₁₇}₂

In a first stage, the lithiated derivative of(perfluorooctyldimethylsilyl)cyclopentadiene is prepared by adding 3.6ml of n-BuLi (5.7 mmol) in hexane dropwise to a solution composed of2.77 g of C₅H₅Si(CH₃)₂C₈F₁₇ in 50 ml of hexane.

A precipitate slowly forms. The reaction medium is stirred for 12 hours.The precipitate is isolated by centrifuging/separating by settling andis then washed twice with pentane (40 ml and then 25 ml). Drying iscarried out under reduced pressure.

2.09 g of Li[C₅H₄Si(CH₃)₂C₈F₁₇] are obtained (yield 75%), which productexists in the form of a white solid.

In a second stage, the metallocene is prepared. 1.26 g ofLi[C₅H₄Si(CH₃)₂C₈F₁₇] (2.3 mmol) are cooled to −78° C. and are thensuspended at −78° C. in 40 ml of THF.

The mixture obtained, which is blue in colour, is added at −78° C. to asolution of 0.44 g of ZrCl₄(THF)₂ (1.2 mmol) in 40 ml of THF.

After stirring at −78° C. for 20 minutes, the solution is reheated toambient temperature and a wine-red solution is obtained. The solution isstirred for 16 hours, during which time the colouring of the solutionchanges to dark orange.

The THF is removed under reduced pressure and the residue is extractedtwice with benzene (40 ml then 20 ml).

After removing the solvent under reduced pressure, 1.05 g of abrown-coloured viscous product are obtained. This product isrecrystallized twice from hot toluene. 0.2 g of metallocene of formulaZrCl₂{C₅H₄Si(CH₃)₂C₈F₁₇}₂ is obtained (yield 13%), which product existsin the form of pale yellow needles.

Use of 1,1′-bis[(dimethyl1H,1H,2H,2H-perfluoro-1-octyl)silylcyclopentadienyl]zirconium [sic]Dichloride, Hereinafter Denoted by CA1, and of the Compound of FormulaZrCl₂{C₅H₄Si(CH₃)₂C₈F₁₇}₂, Hereinafter CA2, in the Polymerization ofEthylene

Procedure:

A one litre reactor is dried for 1 hour in an oven at 80° C. underreduced pressure. The reactor is subsequently connected to apolymerization line and then placed successively under nitrogen andunder reduced pressure at 130° C. until the pressure reaches 4×10⁻²mbar. 200 ml of toluene are introduced into the reactor and thenethylene is introduced, under 5 bar when the precatalyst CA1 is used andunder 6 bar when the precatalyst CA2 is used. The temperature in thereactor is subsequently stabilized at 80° C. 10 μmol of precatalyst CA1or CA2 are weighed out in a first flask and the toluene solution ofmethylaluminoxane (MAO) is weighed out in a second flask in a glove boxand these two flasks are closed with a septum. On the polymerizationline, toluene (25 ml) is added under nitrogen to the flask comprisingthe MAO and the solution is injected into the reactor. Subsequently, thesame procedure is carried out with the flask comprising the precatalyst.The polymerization lasts for 30 minutes and is subsequently halted witha 2N HCl/ethanol mixture. The polymer obtained is washed twice withacetone and dried at 80° C. for 24 hours in an oven under reducedpressure.

The results are reported in Table 1. The molecular masses Mw and Mn aremean values based on at least two GPC measurements per polyethylenesample.

Results:

TABLE 1 [Zr] Molar ratio Activity Mw Mn PI Test Precatalyst (μmol/l)Al/Zr (kgPE · mol⁻¹[Zr] · h · bar⁻¹) (g · mol⁻¹) (g · mol⁻¹) (Mw/Mn) 1CA1 36 545 2 000 88 000 31 000 2.8 2 CA2 40 500 1 900 96 000 17 000 5.8

Although the invention has been described in conjunction with specificembodiments, it is evident that many alternatives and variations will beapparent to those skilled in the art in light of the foregoingdescription. Accordingly, the invention is intended to embrace all ofthe alternatives and variations that fall within the spirit and scope ofthe appended claims. The foregoing references are hereby incorporated byreference.

1. A compound of formulae (I) or (II):[A][Si(R)_(3−n)RF_(n)]_(z)  (I)

in which: A represents a cyclopentadienyl, indenyl or fluorenyl radical;R represents a hydrogen atom, a linear or branched alkyl radical havinga number of carbon atoms ranging from 1 to 40, an alkoxy radical havinga number of carbon atoms ranging from 1 to 10, an aryl radical havingfrom 6 to 20 carbon atoms, an aryloxy radical having from 6 to 10 carbonatoms or an alkenyl radical having a number of carbon atoms ranging from2 to 10; Rf represents a perfluoroalkyl radical C_(x)F_(2x+1)—(CH₂)_(y)—in which x represents an integer ranging from 1 to 20 an y=0, 1, 2 or 3;n=1, 2 or 3; z=1, 2 or 3; B represents a divalent group >MR¹R² or else

in which M represents a carbon atom, a silicon atom, a germanium atom ora tin atom; R¹, R², R³ and R⁴, which are identical or different,represent a hydrogen atom, a linear or branched alkyl radical having anumber of carbon atoms ranging from 1 to 20 or an aryl radical havingfrom 6 to 14 carbon atoms; C represents a cyclopentadienyl,methylcyclopentadienyl, pentamethylcyclopentadienyl,butylcyclopentadienyl, indenyl, naphthyl or fluorenyl radical; w=1 or 2.2. A compound according to claim 1, wherein in the formulae of which Arepresents a cyclopentadienyl radical, R represents a methyl radical, Rfrepresents a perfluoroalkyl radical C_(x)F_(2x+1)(CH₂)_(y)— in which x=6or 8 and y=0 or 2, B=>Si(CH₃)₂ and w=2. 3.Dimethyl(1H,1H,2H,2H-perfluoro-1-octyl)silylcyclopentadiene. 4.Dimethyl(perfluorooctylsilyl)cyclopentadiene. 5.1,3-Bis[dimethyl(perfluorooctyl)]silylcyclopentadiene.
 6. The compoundof formula (CH₃)₂Si[C₅H₄Si(CH₃)₂C₈F₁₇]₂.
 7. The compound of formula(CH₃)₂Si[C₅H₃{Si(CH₃)₂C₈F₁₇}₂]₂.
 8. Process for the preparation of thecompounds of formula (I) [A][Si(R)_(3−n)RF_(n)]_(z) according to claim 1the formulae of which y is other than zero, comprising preparing alithiated derivative in a nonpolar solvent at a temperature of between0° C. and 20° C. and in then reacting the said lithiated derivative,dissolved in an ether at low temperature, with a perfluorohalosilane inethereal solution.
 9. Process for the preparation of the compounds offormula (I) [A][Si(R)_(3−n)RF_(n)]_(z) according to claim 1 in theformulae of which y=0, comprising: a) preparing a compound of formulaHSi(R)_(3−n)(C_(x)F_(2x+1))_(n) from C_(x)F_(2x+1)I, BuLi and HSi(R)_(3−n)Cl_(n) at low temperature in solvent medium; b brominating thesaid silane HSi(R)_(3−n)(C_(x)F_(2x+1))_(n) at a temperature in theregion of 60° C. in CCl₄, then c) reacting the brominated compoundobtained BrSi(R)_(3−n)(C_(x)F_(2x+1))_(n) with a lithiated derivative ofA.
 10. A metallocene of formulae (III) or (IV):

in which: B represents a divalent group >MR¹R² or else

in which M represents a carbon atom, a silicon atom, a germanium atom ora tin atom; R¹, R², R³ and R⁴, which are identical or different,represent a hydrogen atom, a linear or branched alkyl radical having anumber of carbon atoms ranging from 1 to 20 or an aryl radical havingfrom 6 to 14 carbon atoms; (I′) represents a cyclopentadienyl radicalhaving one hydrogen less; (C′) represents a cyclopentadienyl,methylcyclopentadienyl, pentamethylcyclopentadienyl,butylcyclopentadienyl, indenyl or naphthyl radical with one hydrogenless, D=(I′) or (C′); M¹ represents a metal from Groups III, IVb, Vb orVIb and a metal from the group of the lanthanides or actinides; L, whichis identical or different, represents a halogen atom, a linear orbranched alkyl radical having a number of carbon atoms ranging from 1 to20, an alkenyl radical having from 2 to 20 carbon atoms, an alkoxyradical having from 1 to 20 carbon atoms or an aryloxy or aryl radicalhaving from 6 to 40 carbon atoms; t represents an integer ranging from 1to 4 and is equal to 2 when, in the formulae (III) and (IV), M¹=Ti, Zror Hf; w=1 or
 2. 11. A metallocene according to claim 10, wherein informula (IV): M¹=Zr, L=Cl, t=2(I′)=(CH₃)₂Si[C₅H₄Si(CH₃)₂(CH₂)₂(CF₂)₅CH₃] or(CH₃)₂Si[C₅H₄Si(CH₃)₂C₈F₁₇]; B=(CH₃)₂Si<.
 12. Process for the productionof polyolefins by polymerization of at least one olefin in the presenceof a catalyst comprising a compound of formula (III) or (IV) from claim10 and at least one cocatalyst.
 13. Process according to claim 12,wherein the cocatalyst is an aluminoxane.
 14. Process according to claim13, wherein the aluminoxane is methylaluminoxane (MAO).
 15. Processaccording to claim 12, wherein the olefin has the formulaR^(α)—CH═CH—R^(β), in which R^(α) and R^(β), which are identical ordifferent, represent a hydrogen atom, a halogen atom, a linear orbranched hydrocarbon radical having a number of carbon atoms rangingfrom 1 to 20 or a phenyl radical optionally substituted by a halogenatom or a linear or branched alkyl radical having a number of carbonatoms ranging from 1 to
 4. 16. Process according to claim 15, whereinthe olefin R^(α)—CH═CH—R⁶² is ethylene.
 17. Process according to claim15, wherein the hydrocarbon radical contains from 1 to 10 carbon atoms.